1. Field of the Invention
This invention relates to a method for stabilizing recombinant DNA molecules and enhancing the expression thereof wherein a strain of the genus Bacillus carrying a temperature-sensitive mutation associated with the initiation of chromosomal DNA replication is used as the host.
2. Description of the Prior Art
Conventionally, it is recognized that, when a recombinant DNA molecule is introduced into a bacterium of the genus Bacillus used as the host, the recombinant DNA molecule exhibits very low stability and, therefore, loss or deletion of the inserted foreign DNA fragment may occur during cultivation. In order to prevent such phenomena, it is common practice to use a strain carrying a restriction-deficient mutation or a recombination-deficient mutation (such as recE4 or the like) as the host. However, it has been reported that, even when such a restriction-deficient and recombination-deficient strain is used as the host, the stability of the recombinant DNA molecule is not satisfactorily high and the recombinant DNA itself may undergo recombination during cultivation to take a form different from the original one [Teruo Tanaka, J. Agr. Chem. Soc. Japan, 56, 811, (1982)].